Visual cortex in the macaque monkey occupies more than half of the cerebral hemisphere and is subdivided into may distinct visual areas--more than two dozen by the latest reckoning. This aims of the proposed research are to characterize the function, connections, and internal organization of a number of extrastriate visual areas in the occipital, parietal, and temporal lobes. This approach is relevant to our understanding of human visual cortex and may ultimately be beneficial for the diagnosis and treatment of strokes, epilepsy, and other cerebral disorders. One project will be to study the modular organization of visual area V2, an area that contains a repeating array of stripe-like compartments. Anatomical techniques will be used to determine how different compartments are connected with each of seven visual areas to which V2 is know to project. Physiological recordings will be used to ascertain the receptive field properties of cells belonging to clusters projecting to different target areas. These experiments should add to our understanding of the strategies used for parallel information processing in the visual pathway. A second project will be to characterize relatively unexplored visual areas in the temporal and parietal lobes. Anatomical pathway-tracing procedures will be used to determine the inputs and outputs of areas PIP, VIP, and LIP in the intraparietal sulcus and areas MST and FST in the superior temporal sulcus. The results should reveal whether higher levels of the visual pathway are organized in hierarchical fashion, as has been inferred for lower levels on the basis of anatomical connectivity patterns. A third project will be to determine how the geometry of visible surfaces is analyzed and represented within visual cortex. Using a video graphics system, simulations of surfaces in 3-dimensional space will be presented while monitoring the responses of single neurons in areas V4 and MT. The hypothesis to be tested is that the activity of individual neurons may be systematically modulated by changes in surface slant and tilt. If so, this would suggest that information about surface orientation is made explicit in extrastriate cortex, much as information about the orientation of 2-dimensional contours is made explicit in primary visual cortex. These experiments should help to reveal how information from a pair of 2-dimensional retinal images is transformed into our perceptions of a 3-dimensional world.